I think the premise leading to the sentence is absurd: "And, if I pretended not to notice these slights, wasn’t I proving that I really was a disengaged, privileged oppressor?".

But the author is trying to reason with her anger in the face of perceived slights - verbalise it or hold it inside?

Epictetus suggests that small losses (of wine or of 'face') should simply be forgotten. They are sunk-costs whose expense has been incurred.

One need not pay more - in the form of one's tranquility or contentment - by dwelling on them.